Assay test kits currently are available for testing a wide variety of medical and environmental conditions or compounds, such as a hormone, a metabolite, a toxin, or a pathogen-derived antigen. Most commonly, these tests are used for medical diagnostics either for home testing, point of care testing, or laboratory use. For example, lateral flow tests are a form of immunoassay in which the test sample flows along a solid substrate via capillary action. Some tests are designed to make a quantitative determination, but in many circumstances all that is required is a positive/negative qualitative indication. Examples of such qualitative assays include blood typing, most types of urinalysis, pregnancy tests, and AIDS tests. For these tests, a visually observable indicator such as the presence of agglutination or a color change is preferred.
A common problem with lateral flow assay test strips is that different test strips tend to produce slightly different results. Unfortunately, no two test strips will perform exactly alike (i.e. generate identical test result values) even if the test strips have the same amount of reagent embedded therein, and even if they are both exposed to the same amount of analyte. Such discrepancies in lateral flow assay test results may be explained by differences in the physical properties of individual test strips, the components used to read the assay test strip and also by differences in the fluid flow path along through different test strips. For example, the biological materials present on the assay test strip might degrade if the assay is stored in a hot or humid environment. In addition, the chemicals placed on the assay can be variable in their effectiveness simply due to the variations in the manufacturing process.